Adenomas and hyperplastic polyps are polypoid lesions that can occur in any part of the colon. Currently all polyps should be resected endoscopically, however adenomas have the potential to develop into colorectal cancer whereas hyperplastic polyps do not. This approach enables the lesions to be evaluated under the microscope. Currently only the pathological diagnosis can distinguish exactly between adenomas and hyperplastic polyps. Acetic acid (AA) chromoendoscopy is already widely used in order to improve optical determination of mucosal lesions in the upper gastrointestinal tract. In the colon only few studies investigated the impact of AA in differentiating normal mucosa from suspicious mucosa. The aim of the present study is to evaluate the value of spraying acetic acid as an adjunct for optical characterization of colon polyps. Using AA may be beneficial for determining optical diagnoses of colon polyps during real time colonoscopy. This is a single-arm proof of principle study. If colon polyps are found during colonoscopy a 1.5 percent AA solution will be used for chromoendoscopy. Endoscopists are encouraged to use the Narrow Band Imaging (NBI) function of the endoscope prior to the use of AA. After AA is sprayed endoscopists will diagnose the polyp optically. Endoscopists have to predict adenomatous or non-adenomatous histology based upon optical features of the polyp. All polyps will be resected endoscopically so that histopathological diagnoses can be determined. After completing the trial the investigators aim to compare optical and histopathological-based diagnoses of polyps. Histopathological diagnoses will serve as the gold standard. Based upon this information the accuracy of the optical diagnoses will be calculated. The investigators hypothesis is, that optical-based diagnosis using NBI and AA will be accurate in > 75% of all polyp cases.